In an in-depth qualitative study of 36 web users, upon seeing advertising for weight loss products on Facebook some female users reported that they assumed that Facebook had profiled them as overweight or fitness-oriented. In fact, these weight loss ads were delivered generically to women aged 24-30. However, because users can be unaware of the impersonal nature of some personalisation systems, such targeted ads can have a detrimental impact on how these users view themselves: to put it crudely, they must be overweight, because Facebook tells them they are.

So maybe Facebook has a lot of power… or maybe we think it has more power than it actually does…